For an 8237-based DMA system, the bus control logic shown in Fig.9-38 must be altered as indicated in Fig.9-54.

The \BHE signal coming out of the 8086 would be latched by the same 8282 as is used by the A19-A16 lines.The A0 line would be connected to the \BHE line through a tristate inverter which is controlled by the 8237's signal.

When AEN is active and a0 =0, \BHE is high, indicating that the transfer is to be made over the lower byte of the bus.If AEN is active and A0 = 1 \BHE is low and the transfer is made over the upper byte.In addition, both the interface and the 8237 must be connected to the bus through extra logic similar to that given in Fig.9-53.